1. Field of the Invention
The present invention relates to a relief valve used for various hydraulic devices such as a master cylinder of brake device for motor vehicles, particularly, to a relief valve having a ball-shaped valve body and a coil spring for biasing the valve body to its seating position, said valve body and coil spring being disposed in a housing forming a passageway for releasing hydraulic fluid.
2. Prior Art
The conventional relief valve belonging to the aforementioned kind of relief valve is disclosed, for example, in the Japanese laid-open patent bulletin of Toku-kai-sho No. 60-45168. In this relief valve, when the hydraulic pressure increases to reach a predetermined degree, the valve body separates from the valve seat and hydraulic fluid is released through a ring gap between the valve body and the housing, thereby preventing any further increase of hydraulic pressure.
The conventional relief valve having the aforementioned construction, however, has a drawback in that it tends to generate a strange peep noise, as the valve body vibrates in the direction of the diameter of the valve seat when the hydraulic fluid is released through the ring gap.